I built this little 7 watt guitar amp out of a Silvertone organ amp. Last night, I plugged it into an ungrounded, three prong outlet in my garage. My girl came in and I put my arm around her while my left hand was holding the strings. I felt the small of her back buzz, and I immediately let go. Unplugged and started testing things. The outlet is wired correctly with the exception of the lack of a ground. Checked polarity with a plug in tester. I measured the voltage from the strings to known ground at about 55V AC. Opened the amp up and did a visual inspection. Can't see anything wrong. The amp works fine. But there's a problem somewhere. For comparison, I plugged my Princeton Reverb into the same outlet with the same guitar&cord combo, and there is no measurable voltage on the strings.